Cryogenic Controls PDF (CAVMC-0514 - Cash Valve

Cryogenic Controls/Pressure Reducing Valves/Pressure Build-Up Regulators
Cryogenics – the science of materials at
extremely low temperatures – has become more
and more important to industry. One important
aspect of this field is the liquification of normally
gaseous elements, including the following,
which are widely used throughout industry:
OXYGEN – Used extensively in BOF furnaces
in the steel industry, for metal cutting, as a
rocket fuel and in medicine.
ACETYLENE – Widely used in welding.
NITROGEN – Used in refrigeration systems, for
metal degassing, in aerosol packaging and in
cryogenic surgery.
HYDROGEN – Used as a rocket propellant and
in the production of several metals.
ARGON – Widely used in incandescent lamps
and fluorescent tubes.
HELIUM – Used for arc welding, in the
manufacture of electron tubes and in cryogenic
research.
CARBON DIOXIDE – Used in refrigeration, to
make aerosol tanks and in fire fighting.
Other cryogenic fluids include liquefied natural
gas, fluorine, krypton, neon, methane and
ethane.
Industrial gases were previously stored in large,
bulky, pressurized metal containers, but now
these gases are stored and shipped in their
liquid state in cryogenic containers called
“Dewars” or converters. Dewars are jacketed
storage vessels that safely maintain liquids at
cryogenic temperatures. The main advantage of
cryogenic containers is a substantial saving of
storage space as demonstrated by the following
example: 162.8 standard cubic feet [4.61 cubic
Construction
Brass forged body and spring chamber; bronze trim and
diaphragms; Teflon® seat disc and diaphragm gasket;
stainless steel pressure spring. All parts are commercially
cleaned for cryogenic service.
NOTE: Also available in stainless steel and special
construction for Hi-Purity service. Contact your sales
representative.
Temperature Rating
+150°F to -320°F [339°K to 78°K]
Maximum Initial Pressure
600 psi [42.18 kg/sq cm]
2
meters] of gas at ambient temperature, when
subjected to a pressure of 2,400 psi [168.72
kg/sq cm] in a pressurized container, will have a
measured volume of one cubic foot [0.028 cubic
meter]; however, 696 standard cubic feet [19.1
cubic meters] of the same gas can be stored in
its liquid state at cryogenic temperatures in a
Dewar with the same measured volume of one
cubic foot [0.028 cubic meter]. This means that,
under cryogenic conditions, the Dewar can
accommodate 4.28 times the quantity of a
normally gaseous element as a pressurized gas
cylinder.
Cryogenic converters are available in a variety
of sizes and shapes and can be either
stationary or installed on over-the-road transport
trucks. They are generally used for liquids with a
boiling point anywhere from -109.3°F [194.7°K]
for carbon dioxide to -452°F [4.3°K] for helium.
Dewars are supplied with inbuilt controls that
allow the material to be drawn as either liquid or
gas. The schematic located on the back cover
illustrates a typical cryogenic container and
controls. While there are many different versions
of this basic system, the components remain
fairly constant. Cash Valve manufactures a
variety of controls for cryogenic systems,
including liquid and gas line-pressure build-up
regulators, economizer (heat leak) back
pressure valves, temperature safety valves,
combination valves, shut-off valves and finalline/service-line
regulators. This data sheet
presents a detailed description of Cash Valve’s
line of cryogenic-service valves.
The Pressure Build-up Circuit
The purpose of the build-up circuit is to maintain
in the converter a pressure approximately 25 psi
[1.76 kg/sq cm] above that required to drive the
liquid to the final vaporizer and to maintain a
pressure differential of approximately 25 psi
[1.76 kg/sq cm] or higher across the service line
regulator. To do this, liquid is drawn into the
pressure build-up coil, where it is warmed by
ambient air and vaporized. The gas then passes
1 the pressure build-up regulator and into the
top of the tank, where it begins to build up
pressure because expansion is limited by the
fixed volume. When this pressure reaches the
set point of the pressure build-up regulator, the
regulator shuts off, stopping vaporization and
pressure build-up. As liquid is forced from the
tank to the final vaporizer, pressure in the tank
begins to drop and the pressure build-up
regulator again begins operating.
The pressure build-up regulator may be located
in the liquid line before the pressure build-up
coil. Since it is now used for liquid rather than
gas service, the regulator may have a smaller
orifice or be a smaller-sized valve. The operation
of a liquid pressure build-up regulator is the
same as that of a gas regulator with the
exception that it regulates the liquid flow before
the pressure build-up coil rather than the gas
flow after the coil. When pressure in the tank
drops, the liquid pressure build-up regulator
opens, allowing liquid to flow through the
pressure build-up coil and vaporize.
Cash Valve manufactures pressure build-up
regulators for most cryogenic system
applications. The Type A-32 is a small (1/4",
8 mm) pressure build-up valve; the larger
Type B, Type G-60 and Type E-55 can be used
for either liquid or gas. The Type B is available
in sizes from 1/4" to 2" [8 mm to 50 mm], the
G-60 from 1/4" to 11/2" [8 mm toh 40 mm] and the
Type E-55 from 11/4" to 2" [32 mm to 50 mm].
A-32 Pressure Reducing or Pressure Build-Up Service ____________________________
Reduced Pressure Ranges
Maximum Working
Spring Pressure
Number psi [kg/sq cm]
4764 2-25 [0.14-1.76]
4765 15-65 [1.05-4.57]
12447 40-100 [2.81-7.03]
12108 50-150 [3.52-10.55]
7337 75-175 [5.27-12.30]
10661 100-250 [7.03-17.58]
— 200-400 [14.06-28.12]
— 300-600 [21.09-42.18]
Dimensions
Dimensions Shipping
Size A B C Weight
inches [mm] inches [mm] inches [mm] inches [mm] lbs (kgs)
1/4 [8] 21/4 [57.15] 33/16 [80.96] 5/8 [15.88] 11/8 (0.51)
3/8 [10] 21/4 [57.15] 33/16 [80.96] 5/8 [15.88] 11/8 (0.51)
A
B
C
CAVMC-0514